/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.ml.common.distance;

import org.apache.flink.ml.linalg.VectorWithNorm;
import org.apache.flink.util.Preconditions;

/** Manhattan distance (also known as L1 distance) between two vectors. */
public class ManhattanDistanceMeasure implements DistanceMeasure {

    private static final ManhattanDistanceMeasure instance = new ManhattanDistanceMeasure();
    public static final String NAME = "manhattan";

    private ManhattanDistanceMeasure() {}

    public static ManhattanDistanceMeasure getInstance() {
        return instance;
    }

    @Override
    public double distance(VectorWithNorm v1, VectorWithNorm v2) {
        Preconditions.checkArgument(v1.vector.size() == v2.vector.size());
        double sum = 0;
        for (int i = 0; i < v1.vector.size(); i++) {
            sum += Math.abs(v1.vector.get(i) - v2.vector.get(i));
        }
        return sum;
    }
}
